Although urea water is used as a liquid reducing agent for reducing nitrogen oxides in exhaust gas of an internal combustion engine, when the thermal decomposition temperature of this urea water is about 150° C. and the freezing temperature of the urea water is −11° C. in a urea concentration of 32.5% (trade name: AdBlue), in the related art, this urea water is often arranged in the vicinity of a heat source so as to warm a reducing agent tank for anti-freezing. For example, in terms of vehicle layout, the reducing agent tank may be arranged at a side of a high-temperature object, such as an engine.
A reducing agent injector is installed in the vicinity of an exhaust pipe, such as a muffler, from the feature of an exhaust gas treatment device, and consequently, the temperature of the reducing agent injector itself also becomes high.
In traveling vehicles, such as a truck, the reducing agent injector, the muffler, or the like, is cooled by wind during traveling. However, in machineries that perform stationary work, such as a hydraulic shovel, an engine room is easily filled with heat, and the temperature of the engine room becomes high easily.
When the reducing agent tank is arranged in a place like machine rooms, such as an engine room, of which the temperature becomes extremely high, the thermal decomposition temperature of the urea water is approached and consequently, there is a concern about degradation of performance. If the reducing agent supplied to a fuel injection device is not managed at a suitable temperature, there is a concern that the liquid reducing agent may reach its thermal decomposition temperature before being injected into the exhaust gas treatment device. In areas where the temperature of outside air is high, the need for cooling the liquid reducing agent increases further.
In the related art, in a machine body of a machinery, such as a hydraulic shovel, a tank housing space is provided inside a counter weight adjacent to an engine room, a tank housing room partitioned off from a weight adjusting material within the counter weight by a partitioning member is formed within this tank housing space so as to be openable and closable by a door, the reducing agent tank is fixed within this tank housing room, a communication opening portion that allows the tank housing room and the outside to communicate with each other is provided with a movable louver that opens and closes a communication opening portion, a fan is provided to control the movable louver according to the temperature within the reducing agent tank or the like or to discharge the air within the tank housing room to the outside or introduce outside air into the tank housing room, and the fan is controlled according to the temperature within the reducing agent tank or the like (for example, refer to PTL 1).